title: Validity and timeliness of syndromic influenza surveillance during the autumn/winter wave of A (H1N1) influenza 2009: results of emergency medical dispatch, ambulance and emergency department data from three European regions.
abstract: BACKGROUND
  Emergency medical service (EMS) data, particularly from the emergency department (ED), is a common source of information for syndromic surveillance. However, the entire EMS chain, consists of both out-of-hospital and in-hospital services. Differences in validity and timeliness across these data sources so far have not been studied. Neither have the differences in validity and timeliness of this data from different European countries. In this paper we examine the validity and timeliness of the entire chain of EMS data sources from three European regions for common syndromic influenza surveillance during the A(H1N1) influenza pandemic in 2009.
  
  
  METHODS
  We gathered local, regional, or national information on influenza-like illness (ILI) or respiratory syndrome from an Austrian Emergency Medical Dispatch Service (EMD-AT), an Austrian and Belgian ambulance services (EP-AT, EP-BE) and from a Belgian and Spanish emergency department (ED-BE, ED-ES). We examined the timeliness of the EMS data in identifying the beginning of the autumn/winter wave of pandemic A(H1N1) influenza as compared to the reference data. Additionally, we determined the sensitivity and specificity of an aberration detection algorithm (Poisson CUSUM) in EMS data sources for detecting the autumn/winter wave of the A(H1N1) influenza pandemic.
  
  
  RESULTS
  The ED-ES data demonstrated the most favourable validity, followed by the ED-BE data. The beginning of the autumn/winter wave of pandemic A(H1N1) influenza was identified eight days in advance in ED-BE data. The EP data performed stronger in data sets for large catchment areas (EP-BE) and identified the beginning of the autumn/winter wave almost at the same time as the reference data (time lag +2 days). EMD data exhibited timely identification of the autumn/winter wave of A(H1N1) but demonstrated weak validity measures.
  
  
  CONCLUSIONS
  In this study ED data exhibited the most favourable performance in terms of validity and timeliness for syndromic influenza surveillance, along with EP data for large catchment areas. For the other data sources performance assessment delivered no clear results. The study shows that routinely collected data from EMS providers can augment and enhance public health surveillance of influenza by providing information during health crises in which such information must be both timely and readily obtainable.
authors.affiliation: Department of International Health, CAPHRI School for Public Health and Primary Care, Faculty for Health, Medicine and Life Sciences, Maastricht University, Duboisdomein 30, Maastricht 6229 GT, The Netherlands. nicole.rosenkoetter@maastrichtuniversity.nl.
authors.forename: Nicole
authors.initials: N
authors.lastname: Rosenkötter
authors.forename: Alexandra
authors.initials: A
authors.lastname: Ziemann
authors.forename: Luis Garcia-Castrillo
authors.initials: LG
authors.lastname: Riesgo
authors.forename: Jean Bernard
authors.initials: JB
authors.lastname: Gillet
authors.forename: Gernot
authors.initials: G
authors.lastname: Vergeiner
authors.forename: Thomas
authors.initials: T
authors.lastname: Krafft
authors.forename: Helmut
authors.initials: H
authors.lastname: Brand
mesh_terms: D000552:Ambulances; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005060:Europe / Q000453:epidemiology; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification; D007251:Influenza, Human / Q000453:epidemiology* / Q000628:therapy; D062486:Public Health Surveillance / Q000379:methods*; D015203:Reproducibility of Results; D012621:Seasons